In the aforementioned application of Edward M. Kaucic, there is disclosed and claimed a vertical blind mechanism comprising a rod having lengthwise extending track means and a lead carrier and a plurality of auxiliary carriers are mounted on the track means for movement along the rod. A vane support is mounted on each auxiliary carrier for turning about an upright axis and a sprocket is mounted for axial rotation on each vane carrier and connected through drive means to the associated vane support for turning the latter. A chain return means is provided on the lead carrier and a flexible chain is looped intermediate its ends around the chain return means and has first and second chain portions extending from the chain return means lengthwise of the rod toward one end of the latter. First and second chain guide means are provided on each auxiliary carrier for retaining the first and second chain portions in meshing engagement with the associated sprocket at diametrically opposite sides thereof. A traverse means is connected to the lead carrier for moving the lead carrier along the rod between a retracted position adjacent said one end of the rod and an extended position spaced along the rod from said retracted position and means are provided for releasably retaining the lead carrier in its extended position on the rod with the first and second chain portions drawn lengthwise of the rod. The first and second chain portions limit maximum separation between the carriers when the lead carrier is moved in one direction along the rod away from said one end to said extended position, and chain operation means associated with the ends of said first and second chain portions is operable to relatively move said first and second chain portions lengthwise in relatively opposite directions for rotating the sprockets to turn the vanes when the lead carrier is in its extended position.
When the carriers are in a partial or fully retracted condition on the rod, the first and second portions of the chain form loops between adjacent carriers. If the chain operating means is operated to move the chain portions in relatively opposite directions for rotating the slats when the carriers are in a partially or fully retracted condition, the slack loops in the chain portions sometimes become entangled or looped around other parts.